1. Field of the Invention
The present invention relates to an optical fiber suitable as a transmission line of a wavelength division multiplexing (WDM) transmission system for transmitting multiplexed signals of a plurality of channels having wavelengths different from each other.
2. Related Background Art
A wavelength division multiplexing (WDM) transmission system is a system for transmitting multiplexed signals (WDM signals) of a plurality of channels included in a predetermined signal wavelength band, and makes it possible to transmit and receive a large capacity of information. Conventionally, signal wavelength bands in which WDM transmissions are carried out have been in the wavelength range of 1530 nm to 1565 nm, and optical fibers employed in a transmission line have been designed so as to have an optimal characteristic in this wavelength range (e.g., U.S. Pat. No. 5,327,516). Recently, the wavelength range of 1565 nm to 1625 nm, which is on the longer wavelength side than the above-mentioned wavelength range, and the wavelength range of 1440 nm to 1530 nm, which is on the shorter wavelength side than the above-mentioned wavelength range, have been under consideration as a signal wavelength band in which WDM transmissions are to be carried out, whereby optical fibers having favorable characteristics in these wavelength ranges have been proposed as well.